The invention relates to the field of nano-electronics and is directed to a four terminal nano-electromechanical switch.
As power and energy constraints in microelectronic and nano-electronic applications become more and more challenging, one is seeking constantly alternative and more power efficient ways of switching and computing. A conventional switching device used in the semiconductor industry is a CMOS transistor. To overcome power related bottlenecks in CMOS devices, switching devices which operate on fundamentally different transport mechanisms such as tunneling are investigated. However, combining the desirable characteristics of high on-current, very low off-current, abrupt switching, high speed as well as a small footprint in a device that might be easily interfaced to a CMOS device is a challenging task. Mechanical switches such as nano-electromechanical switches (NEM switches) are promising devices to meet these kinds of criteria. A nano-electromechanical switch having a narrow gap between electrodes is controlled by electrostatic actuation. In response to an electrostatic force, a contact electrode can be bent to contact another electrode thus closing the switch. The control of the narrow gap for the electrostatic actuation and for the electrical contact separation is a main issue in designing and operating nano-electromechanical switches. A nano-electromechanical switch has to meet both, the requirement of high switching speed and low actuation voltage.
On the other hand, both three and four terminal switches are investigated, but four terminal switches offer more possibilities to circuit designers and are consequently investigated in priority. A four terminal switch indeed enables the control of the switching state (open/close) by a gate-to-body voltage independent of the source and the drain voltage. This is of great interest in many application scenarios, such as body-biasing schemes or for adiabatic logic.
Yet, four terminal switches described in the literature are bulky, with multiple large contact pads and poor scalability, like the ones described in Nathanael et Al., “4-terminal relay technology for complementary logic”, Proc. IEEE Int. Electron Devices Meeting (IEDM), 2009.
The document U.S. Pat. No. 8,018,308 discloses a micro-electromechanical switch and a method for fabricating the same. From U.S. Pat. No. 8,018,308, it is known a downward type micro-electromechanical switch including a substrate in which a first cavity and a second cavity are formed. A first fixing line and a second fixing line are formed on an upper surface of the substrate not to be crossed with the first cavity and the second cavity. A contact pad is spaced apart at a predetermined distance from surfaces of the first fixing line and the second fixing line. A first actuator and a second actuator are disposed on each upper portion of the first cavity and the second cavity and downward actuate the contact pad to be in contact with at least one of the first fixing line and the second fixing line when power is supplied.
Within this context, there is still a need for an improved low power nano-electromechanical switch to reduce the power consumption in the switch, whereas the contact pad disclosed in prior art four terminal electromechanical switches are bulky and are sources of energy loss.